3
Adjustment
The best performance is obtained by connecting a greyscale/mulitiburst video generator to the
video transmitter BVT 225 and oscilloscope and a monitor to the receiver or the receiver part of the
BVX-225. On the receiver check that H1 line status indication (green LED) is flashing. The yellow
LED H2 indicates power.
If a negative or turned over picture is displayed on the monitor, the twisted pair cable should be
reversed at the receiver input terminal X1.
If the transmission line includes a BVX-225 repeater, the two twisted pair lines should be treated as
two individual twisted pair lines - the only issue to be considered is the order in which the individual
units are adjusted:
1. Video transmitter BVT-225.
2. Receiver part of BVX-225.
3. Transmitter part of BVX-225.
4. Video receiver BVR-225.
Several BVX-225 repeaters can be inserted in a line to extend the transmission distance further.
However, a certain decrease of video quality must be expected.
3.1
Cable impedance settings
The cable impedance setting should be set in accordance with the characteristic impedance of the
twisted pair cable used in order to avoid signal reflections (shadows in the picture).
Cable impedance
BVT-225 & BVX-225
switch S1
Cable impedance
BVR-225 & BVX-225 jumper W1
Pos.
Description
Position
Description
H
124
Ω
for 90-140
Ω
cables
124 (pins 1-2)
124
Ω
for 90-140
Ω
cables
L
62
Ω
for 50-70
Ω
cables
62 (pins 2-3)
62
Ω
for 50-70
Ω
cables
3.2
Setting of unbalanced output voltage for BVT-225
It is possible to choose between two values for unbalanced output voltage:
Unbalanced output voltage:
BVT-225: jumper W2
Pos.
Pin no.
Output voltage
Cable length (approx.)
*
1.0
1-2
1.0 Vpp linear
<150m
2.0
2-3
1.2 Vpp, +2 dB @ 5 MHz <300m
*Note:
These settings are determined using the cable type: RG59
3.3
Initial setting for BVT-225 and BVX-225
Under normal circumstances the setting mentioned below only need to be set when the transmitter
or the repeater is installed. However, if the cable quality is either very high or very low, or the cable
distance is not exactly known it may be necessary to alter the transmitter settings at a later stage;
i.e. if impossible to adjust the receiver to the required video quality.
Balanced output voltage:
BVT-225: jumper W1 & BVX-225: jumber W2
Pos.
Pin no.
Output voltage
Cable length (approx.)
*
2.0
2 (or none) 2 Vpp linear
< 1500 meters
3.0
1-2
3 Vpp, +2 dB @ 5 MHz
< 2000 meters
4.0
2-3
4 Vpp, +4 dB @ 5 MHz
> 2000 meters
*Note:
These settings are determined using the cable type: Mödinger A-2Y(L)2Y / 2x2x0,6 mm.
Twisted pair video equipment Series 225
2800-00054
